The invention concerns a method for determining the strength of the welding current to be used for the resistance seam welding of container bodies sequentially following one another. The invention also concerns a welding apparatus for the resistance seam welding of container bodies, with welding rolls, a welding current generator and a welding current control. The invention further concerns a method for the resistance seam welding of container bodies with nonuniform overlapping as well as a welding apparatus for the resistance seam welding of container bodies with nonuniform overlapping.